Mycobacterium tuberculosis Co-opts Monocytic Niches to Evade Immunity in Lymph Nodes

These aggregates exhibited alternative activation profiles and coincided with reduced T cell priming and Th1 differentiation. Strikingly, Mtb-specific T cells appeared unable to engage these infected aggregates, suggesting immunological ‘blindness’ to this niche. BCG vaccination curtailed Mtb burden and limited monocyte aggregate formation in the medLN without significantly altering myeloid trafficking or T cell priming, suggesting that vaccination impairs the formation of the monocytic niche rather than initial dissemination.

Together, these findings reveal a narrow temporal window for effective T cell priming in LNs and identify a later-arising monocytic niche that supports Mtb persistence while evading immune recognition, highlighting how spatially organized host-pathogen interactions govern both protection and persistence during tuberculosis.